How to Install a Flat Threshold
- 1). Open the door and swing it to the inside. Clean out the area where the old threshold was. Brush out any loose debris in the area with a clean rag. Pull up the larger pieces of debris by hand.
- 2). Inspect the area and verify the sheathing underneath is in good shape and not rotted. Check that it is strong enough to support the threshold. Tighten it down in place, if necessary with wood screws and a power drill.
- 3). Put a tube of tri-polymer caulk into a caulk gun. Cut the tip of the nozzle off with a utility knife at a slight upward angle. Line up the caulk gun at either end of the door on the side closest to the interior of the house. Pull the trigger and run a thin bead across the opening in the floor, against the flooring inside the house.
- 4). Set the new threshold into the opening and press down firmly so it can adhere to the caulk underneath. Slide shims underneath the threshold from the outside of the house until it is level across the opening. Close the door and verify the threshold is the proper height.
- 5). Apply a bead of polyurethane sealer under the threshold from the outside of the house. Run the bead straight across under the center of the threshold. Shut the door again and slide shims between the door and the threshold. Leave the shims in place for three hours to prevent the threshold from moving when the sealer expands.
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